This invention relates to a dilatation catheter and more particularly to a monorail type dilation catheter having a stiffening wire.
Monorail dilatation catheters are commonly used in angioplasty procedures because the unique construction of such catheters enables the rapid exchange of the catheter once it is inserted into the patient. For example, U.S. Pat. No. 4,762,129 to Bonzel discloses a monorail catheter having a short tube defining a guide wire lumen at the distal end of the catheter. The tube extends through the balloon from the distal end to a point proximal of the proximal end of the balloon. This tube terminates at an aperture opening to the exterior of the catheter such that most of the length of the guide wire from the balloon to the proximal end of the catheter is exterior of the catheter. Rapid exchange and manipulation of the dilatation catheter is facilitated because the catheter segment contacting the surface of the guide wire is only as long as the balloon.
Although the monorail catheter provides rapid catheter exchange, it tends to lack stiffness and, therefore, is difficult to push through a patient""s blood vessels. In the Bonzel construction, a stiffening wire extends through the catheter imparting stiffness to the catheter. However, the stiffening wire may impart stiffness in areas of the catheter where flexibility is desired, for example in the balloon.
Due to the construction of the catheter, heretofore it has not been feasible to terminate a stiffening wire in a dilatation catheter proximal of the section of the catheter in which flexibility is desired. To provide enhanced flexibility in situations where a stiffening wire is used, tapered stiffening wires have been proposed. Schneider (Europe) AG sells a dilatation balloon catheter in which a tapered stiffening wire xe2x80x9cfloatsxe2x80x9d within the catheter, i.e., the stiffening wire is not anchored at its distal and proximal ends. While this construction, in the ideal situation, may provide the requisite stiffness and maintain distal flexibility, the floating stiffening wire is prone to movement which can lead to problems in manipulating the catheter.
The object of the invention is to provide a dilatation catheter in which a stiffening wire terminates proximal of the distal end of the catheter and is securely anchored in place at both its distal and proximal ends.
A more specific object of the invention is to provide a catheter of the monorail type in which a stiffening wire is anchored at the proximal end of the catheter and wherein the distal end of the stiffening wire terminates at and is secured in place within the catheter in the region of the entrance port for the guide wire.
In accordance with the present invention, a balloon dilation catheter of the monorail type includes a stiffening wire secured at both its ends in a selected position such that maximum strength is imparted in the proximal portion of the catheter while flexibility is maintained in the distal portion of the catheter and the balloon. In the preferred embodiment, the catheter comprises an elongated tubular shaft with a dilatation balloon mounted on its distal end. An inner tube extends distally from a position proximal of the guide wire port and is adapted to receive the guide wire which is inserted through the port. The space between the tubular shaft and the inner tube provides an inflation lumen for the balloon. In accordance with the invention, a stiffening wire is anchored at its proximal end within the catheter and the distal end of the stiffening wire is retained within the inner tube in the vicinity of the guide wire port.